1. Field of the Invention
The invention relates to the use of a piece of adhesive film for a bond which can be separated without damage and without leaving a residue, and to corresponding adhesive bonds.
2. Description of Related Art
Adhesive films which can be detached by pulling in the bond plane are known and are commercially available, for example as POWER STRIPS(copyright) (stretch-release adhesive tape) from Beiersdorf AG.
U.S. Pat. No. 4,024,312, for example, describes a self-adhesive tape having an extensible and elastic support made from a block copolymer, in particular for applications in the medical area, where pain-free removal from the skin is desired.
Furthermore, DE 33 31 016 A1 describes an adhesive film for temporary adhesive bonds which allows an adhesive bond produced therewith to be separated by pulling on the adhesive film in the direction of the bond plane. Adhesive films of this type allow high adhesive strengths and shear strengths to be achieved and adhesive sandwich systems to be separated again without further aids, in a comparable manner to the opening of a preserving jar, where the rubber seal is pulled out of the sealing join via the tab.
Furthermore, DE 37 14 453 C1 describes a practice explosive charge which is temporarily attached to a practice object by means of an adhesive film of this type and can be removed from the practice object without damage.
Furthermore, WO 92/11333 describes, inter alia, adhesive films for corresponding applications where the adhesive films employed have low elasticity at the same time as high extensibility.
DE 42 22 849 C1 likewise describes a strip of adhesive film of this type with a specially designed tab.
Finally, DE 42 33 872 C2 and WO 94/21157 describe redetachable self-adhesive hooks which are likewise provided with adhesive films of this type and are thus redetachable.
However, the adhesive systems described in the above patent specifications also have a number of disadvantages:
In order to facilitate removal of the adhesive film from the bond join, part thereof must project therefrom in the form of a tab. The adhesive film is thus necessarily not completely invisible in the case of the bonding of inflexible objects, but rather the tab is visible, which can appear unattractive and can also result in technical problems when materials which age on exposure to light are used.
During bonding, the entire adhesive film, i.e. including the tab, can easily disappear into the bond join. This can happen, particularly to the inexpert user, if he does not place a piece of adhesive film of this type on the edge of the substrate in such a way that a tab sticks out and then projects out of the bond join. It is then hard to know what to do to release the bond, and destruction, at least of one substrate, can be the consequence.
If the adhesive films tear during the release process and a torn piece of adhesive film remains completely inside the bond join, separation of the bonded materials without leaving a residue and without destruction of bond partners is usually no longer possible, which can cause considerable damage.
It therefore remains an unsolved problem of how valuable articles or those which are to remain undamaged, in particular should not be drilled through, can be attached reversibly and without damage and can be detached again without leaving a residue. For example, children""s glass paintings, decorative tiles, but also heavier articles, are to be hung up temporarily, if possible without a visible tab or a similar foreign body extending beyond or projecting from the bond join. The object of the invention was to provide a solution here.
Accordingly, the invention relates to the use of the adhesive film pieces described at the outset, as characterized in greater detail in the patent claims, and to adhesive sandwich systems characterized in greater detail therein.
Regarding the adhesive film pieces to be employed, reference is made to the cited prior art.
Detachment of the bonded articles is achieved by stretching the double-sided adhesive tape. The loss of adhesion which occurs is favoured by reducing the tack of the contact-adhesive composition analogously to DE 33 31 016 or DE 42 22 849, and by reducing the adhesive film thickness, caused by the stretching of the adhesive film.
For the use of adhesive film pieces with a backing, particularly suitable products are those of the type as in WO 92/11333.
There are many ways of producing the non-adhesive areas for tabs, for example by rendering the contact-adhesive composition inert by means of a non-tacky coating or by lamination with thin layer materials, such as plastic films and papers.
Suitable covering paper or release laminates are conventional release films and release papers, for example silicone-treated release films/release papers, which are usually employed as sheet-like media which have good release properties vis-à-vis contact-adhesive compositions.
Regarding the production, processing and handling of the particularly preferred adhesive films, reference is made in general terms to DE 33 31 016, DE 42 22 849 and WO 92/11333.